The present invention relates to superluminescent (SL) devices, and more particularly, to such devices that are coupled to gratings.
Superluminescent devices, such as diodes are less coherent (broader bandwidth) than laser diodes, and therefore, have less speckle interference patterns that are random in time. For certain applications, such as gyroscopes, this is desirable, since the gyroscope output signal represents a phase difference and any random interference patterns result in phase noise in the output signal. SL devices normally have two ends with a reflecting and antireflecting coatings respectively disposed on the ends. The light is emitted by the end with the antireflecting coating. However, some small amount of light will be reflected from the antireflecting coating resulting in speckle interference patterns, and thus, phase noise in a gyroscope output signal, although less than that when a laser, which has two reflecting coatings, is used therein.
It is, therefore, desirable to have an SL device which has reduced speckle interference patterns, and thus, produces reduced phase noise when used in an application such as a gyroscope.